The UMASK value masks out the bits. The
permissions that each position in the UMASK masks out are the same as the file
permissions themselves. So, the left-most position masks out the owner
permission, the middle position the group, and the right most masks out all
others. If we have UMASK=007, the permissions
for owner and group are not
touched. However, for others, we have the value 7, which is obtained by setting
all bits. Because this is a mask,
all bits are unset. (The way I remember this
is that the bits are inverted. Where it is set in the UMASK, it will be unset in
the permissions,
and vice versa.)
